1. Technical Field of the Invention
The present invention relates to keyboard device having a frame formed of resin in one united body to support a plurality of keys such that the keys can pivot.
2. Description of the Related Art
Conventional keyboard devices have been known in which a frame to support a plurality of keys for allowing the keys to pivot is supported on an instrument main body. In particular, keyboard devices have been known in which the frame is formed of resin in one united body (Patent documents 1 and 2 below).
In a keyboard device, a part functioning as a frame, i.e., a “frame function part” engaging, in contact, with a component excluding the frame during the use of the keyboard device, is provided at the frame in one united body or as a separate body. In Patent documents 1 and 2 below, for example, there are various frame function parts including a stopper to restrict a rotation start position and a rotation end position of a key and a hammer, a key operating guide, a board mount part, and a deck contact part.
Since external force is applied to the portions of the frame where these frame function parts are provided, it is preferable to design the frame such that the frame exhibits high stiffness. For a frame made of resin, such high stiffness is secured generally by providing a sufficient amount of resin to the portions of the frame.
[Patent document 1] Japanese Patent No. 3819136
[Patent document 2] Japanese Patent Application Publication No. H9-244623
When the amount of resin used is increased, however, the cost is increased, and, in addition, the weight is also increased. In Patent documents 1 and 2 above, a plate-shaped member of the frame is large, and the stiffness is also high. However, the amount of resin used is large, and therefore, improvement thereof is necessary. Also, it is necessary to consider the arrangement positions of the frame function parts in addition to the reduction of the amount of resin while appropriately securing the stiffness.